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Make average line length example more concise and move it to the top #1711

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Merged
merged 2 commits into from
Jun 21, 2017
Merged

Make average line length example more concise and move it to the top #1711

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432eb1b
Make average line length example more concise
PetarKirov Jun 17, 2017
634f9a3
Copy the average length example to the top
PetarKirov Jun 17, 2017
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38 changes: 28 additions & 10 deletions index.dd
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,27 @@ $(DIVC intro, $(DIV, $(DIV,
)
$(DIVID your-code-here-default,
$(RUNNABLE_EXAMPLE
$(RUNNABLE_EXAMPLE_STDIN
The D programming language
Modern convenience.
Modeling power.
Native efficiency.)
----
// Compute average line length for stdin
void main()
{
import std.range, std.stdio;

auto sum = 0.0;
auto count = stdin.byLine
.tee!(l => sum += l.length).walkLength;

writeln("Average line length: ",
count ? sum / count : 0);
}
----
)
$(EXTRA_EXAMPLE
$(RUNNABLE_EXAMPLE_STDIN 2.4 plus 2.4 equals 5 for sufficiently large values of 2.)
----
// Round floating point numbers
Expand Down Expand Up @@ -243,20 +264,17 @@ Modern convenience.
Modeling power.
Native efficiency.)
----
#!/usr/bin/env rdmd
import std.range, std.stdio;

// Compute average line length for stdin
void main()
{
ulong lines = 0, sumLength = 0;
foreach (line; stdin.byLine())
{
++lines;
sumLength += line.length;
}
import std.range, std.stdio;

auto sum = 0.0;
auto count = stdin.byLine
.tee!(l => sum += l.length).walkLength;
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@CyberShadow CyberShadow Jun 17, 2017 •
edited
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Even shorter would be:

size_t count = 0;
double sum = stdin.byLine.tee!(l => count++).sum;

but I guess that demonstrates fewer range features.

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@PetarKirov PetarKirov Jun 18, 2017 •
edited
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I don't think that would compile, unless you add a map!(l => l.length) between the tee and the sum.

/d912/f975.d(7): Error: template std.algorithm.iteration.sum cannot deduce function from argument types !()(Result), candidates are:
/opt/compilers/dmd2/include/std/algorithm/iteration.d(4663): std.algorithm.iteration.sum(R)(R r) if (isInputRange!R && !isInfinite!R && is(typeof(r.front + r.front)))
/opt/compilers/dmd2/include/std/algorithm/iteration.d(4674): std.algorithm.iteration.sum(R, E)(R r, E seed) if (isInputRange!R && !isInfinite!R && is(typeof(seed = seed + r.front)))

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@CyberShadow CyberShadow Jun 21, 2017

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Oops, you're right :)


writeln("Average line length: ",
lines ? cast(double) sumLength / lines : 0.0);
count ? sum / count : 0);
}
----
))
Expand Down